The present application represents a systematic extension of funded studies by the PI on MDMA use in young adult (18-29 y/o) university students. The major goal is to evaluate residual central nervous system (CNS) effects of previous Ecstasy (MDMA or 3, 4-methylenedioxymethamphetamine) use in young adults. Considerable evidence suggests that MDMA can substantially affect serotonergic reuptake because its repletion mechanisms may be permanently altered. This outcome appears to produce deficits in cognitive processes, although the source of the effects is debated. The present application will employ sensory evoked potential (EP) auditory brainstem responses (ABRs), cognitive event-related brain potentials (ERPs), and electroencephalographic (EEG) paradigms to assess the CNS functional effects of MDMA use by comparing well-defined subject groups: (1) non-using Controls, (2) primarily Ecstasy users, and (3) Ecstasy-Plus (+) mpoly-drug users. Preliminary Studies indicate that these neuroelectric measures reveal considerable CNS drug-related damage. The application is organized around two approaches: STUDY 1 will assess the 3 subject groups using previously successful sensory EP and new cognitive ERP paradigms. The goal is to refine the measures and findings in order to identify the possible sources of neurocognitive insult from Ecstasy. STUDY 2 will assess non-use Control and Ecstasy users who vary systematically in the amount and recency of MDMA use in attempt to quantify the possible long-term effects of Ecstasy intake. Equal numbers of female and male subjects will be assessed in all phases. The proposed methods will characterize CNS differences from MDMA use to provide assessment of drug effects on cognition.